The present invention relates to an improvement of a color television tube assembly of the type comprising a color television tube with three in-line electron guns for producing three electron beams in the same horizontal plane, a horizontal deflection yoke mounted on the color television tube for producing the pincushion-like horizontal deflection magnetic field and a vertical deflection yoke mounted on the tube for producing the barrel-like vertical deflection magnetic field.
The so-called self-convergence in-line electron gun type color television tube in which the horizontal deflection magnetic field with the pincushion distortion and the vertical deflection magnetic field with the barrel distortion are produced has an advantage that a dynamic convergence circuit may be eliminated. However, the electron beam from each electron gun is distorted when it passes through the pincushion distorted horizontal deflection magnetic field and the barrel distorted vertical deflection magnetic field so that the beam spot especially at the edge of the screen is distorted in the form of an ellipse. In general, the further the electron beam is away from the axis of the tube, the more strongly the beam is deflected in the horizontal direction. Therefore, the larger the horizontal deflection angle, the more the beam spot at the screen is elongated in the horizontal direction. On the other hand, the closer the electron beam is to the axis of the tube, the more strongly the beam is deflected in the vertical direction. Therefore, the larger the vertical deflection angle, the more the beam spot at the screen is elongated in the horizontal direction. The larger the deflection angle of a color television tube, the greater the beam distortion or aberration becomes especially at the edge of the screen.